Electrical Impedance Tomography (EIT) is a technique for obtaining images that is based on the application of alternating electrical signals whose frequencies range between 10 kHz and 2.5 MHz on a patient's body surface. The device used to this end comprises a plurality of electrodes (e.g., electrodes 1030 in FIG. 10) placed in contact with the skin, which are connected through electric conductors to a processing unit that produces the signal. The method used comprises a plurality of steps in each of which a pair of electrodes is selected for the signal injection, while induced voltages are measured at the electrodes that are not being used for the signal injection. In the following steps, other pairs of electrodes for signal injection are selected, continuing the sequence until all the electrodes of the device are selected, completing an exploration cycle. The induced voltages that were captured by electrodes are submitted to a treatment through a specific software, allowing the production of images that represent ventilation and perfusion phenomena in the body of interest.
One of the great advantages of the Electrical Impedance Tomography over the pneumotachograph, for instance, is that as the EIT generates images, it provides the user regional information of the body under study.
However, in conformity with the prior art, the images are shown in their highest possible resolution, in which each pixel has its corresponding impedance value. Algorithms to filter the noise and improve the image are used, but always seeking to determine the value of each pixel in order to show it in the image.
Despite the effort to develop increasingly more precise EIT devices, a great challenge is still represented by the capacity of interpretation and users' use of the information generated by this device. Even skilled physicists and physiotherapists find the interpretation of these images difficult. This is a limitation for the use of this technology, which, if widely used, would allow a significant increase in the patient survival by allowing the adjustment of ventilator and hemodynamic parameters and appropriate maneuvers.
U.S. Pat. No. 7,435,226, entitled METHOD AND APPARATUS FOR DISPLAYING INFORMATION OBTAINED BY ELECTRICAL IMPEDANCE TOMOGRAPHY DATA, describes various screen modes and suggests graphics and numerical values as a way to achieve data reduction to aid image interpretation. The data used to generate the images are processed in a different manner to calculate and display the graphic and numerical values.
The attempt to show the information of the image in a graphic or numerical format is valid, but it does not improve the image itself that, as said, is the main advantage of EIT. Conversely, construction and multiple graphs, one for each region of interest, involve a higher level of difficulty for the user, instead of facilitating the cognitive effort to interpret the images. This is even more important in those cases in which the space reserved to EIT data is limited, for instance, in EIT modules that use the screen of the device already installed in the Intensive Care Unit, such as a monitor or ventilator, for example.
U.S. Patent Application Publication 2009/0024008, entitled METHOD AND APPARATUS FOR SIMPLIFYING DIAGNOSTIC ASSESSMENT OF A MECHANICALLY VENTILATED PATIENT, requires the collection of parameters of different origin as it builds an illustration of the lung therefrom, which is either increased or decreased depending on the volume and rate of ventilation.
The lung illustration aims at giving the user a qualitative picture of the acquired physiological parameters. Although, at first sight, it looks like an interesting idea, this technology leads to the creation of new graphical elements (images) from a numerical value, requiring users to consider these two types of representation.
International Publication WO 2012/007425, entitled METHOD AND APPARATUS FOR TIME-BASED ANALYSIS OF ELECTRICAL IMPEDANCE TOMOGRAPHY DATA, describes a method and apparatus in which an EIT image comprises one or a plurality of pixels that represent a specific impedance value or even a specific PAT (Pulse Arrival Time) value, calculated for pixels or a set of pixels. Since a plurality of pixels has the same underlying value, it is natural that this set is represented in the same manner. However, this does not solve the problem to simplify the graphical representation, using a set of pixels with different impedance values, presented in a uniform manner, depending on a condition, event or trend identified in this region, composed of this set of pixels.
U.S. Patent Application Publication 2012/0228143, entitled APPARATUS AND METHOD TO DETERMINE FUNCTIONAL LUNG CHARACTERISTICS, describes an apparatus and a method to determine the functional characteristic of the lung, through Electrical Impedance Tomography. From the regions of interest, the ratio between the impedance in this region and the global impedance is calculated for each region, resulting in graphs and indexes that present these ratios. The above-mentioned document does not state that such indexes are represented in the image itself through a uniform representation of the region of interest. On the contrary, it refers to numerical indexes and graphs that do not improve the image itself, involving a higher level of difficulty for the user.
Thus, it is evident that the prior art does not result in a simplification of the image, as it does not provide additional ways to represent or reduce the information.